For me, the word 'floor' indicates somewhere inside a building (OK, forget a 'valley floor' for the moment!) and the word 'ground' indicates somewhere outside a building.
So if someone finds something on 'the floor', I expect that they're referring to somewhere inside their house/inside a shop/office etc.
But it appears that many people now think that 'the floor' can indicate on the pavement/road/in the park etc, whereas I'd use the word 'ground' in those scenarios.
Is anyone else in agreement with me - or am I going to be flamed for not keeping up with modern usage?!